Drill bit



D. J. GRADY April 5, 1960 DRILL BIT Filed Dec) so, 1957 April 5, 1960 D. J. GRADY 2,931,630

DRILL. BIT

Filed Dec. 50, 1957 2 Sheets-Sheet 2 ATTORNEYS DRILL BIT Daniel J.` Grady, Shreveport, La., assigner to Hycalog, Inc., Shreveport, La., a corporation of Delaware Application December 30, 1957, Serial No. 705,865 1o Claims. (ci. zss-sn This invention relates to a drill bit of the type having diamonds or the like fixed thereto for cutting or abrading away an earthen formation. In one of its aspects, it relates to a bit of this type having an improved arrangement for vremoving formation atethe center rof the bore hole. ..7

One ofthe principal problems encountered iu the design of a .diamond drill bit is the provision of an efficient cutting arrangementat the center of the bore hole. The diamonds positionedA 'at or adjacent to the gage cutting surfaces of the bit travel at a relatively high lineal speed and hence their cutting action is relatively rapid. However, as the center of the bit is approached, the diamonds travel at slower and slower lineal speeds so that the cutting eiciency at, or close to, the center of rotation is considerably less than that at the periphery of the bit. Accordingly, the cutting efliciency at the center frequently establishes the penetration rate forv the bit.

Several Vdifferent approaches have been made in an attempt to increase the center drilling efficiency of this type of bit. One approach has been to increase the effective areaof the cutting surface ofv the bit at its center by extending or recessing the center surface into conical shapes. vThe conical recess is more generally used'because it is easier to flush drilling lluid over the surface of a recess from a central passageway in the bit. However, the use of such recesses has generated another problem. Thus, the cone of formation material in the recess frequently breaks off or fractures horizontally leaving a loose conical piece of formation in the cone recess. The broken olf piece of formation turns or `spins with the bit rather than being Aground in to pieces by the diamond cutting elements intheV recess. This .greatlyf reduces the penetration rate because the brokenoff piece of formation must be slowly wornv away by the formation under it, or crushed by the bottom holeweight on the bit or released by raising the bit from the bottom of the hole. In formations where such `fractures are common, it" can be seen that the provision of the conical recess may reduce'the efficiency of the bit rather than increase it.

A principal object of this invention is to provide a diamond type bit which in use deliberately forms a central'core from the formation and -then breaks olf this core and flushes the same from the bit. Thus, the center of the hole being drilled is not actually cut away but rather is removed as a series of deliberately formed cores so that thepenetration rate of the bit does not depend upon theefciency of cutting at its central axis.

Another object is to provide such a bit wherein the pressure of the drilling mud or fluid is utilized to break olf,- or aid in breaking olf, the central core of the formation after which such uid flushes the broken off core from the bit.

Patented Apr. 5,1960

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Another object is to provide such a bit with a flushing fluid arrangement wherein a major portion of the fluid tends to ow into the core receiving recess, but, as the core begins to form, it creates an obstruction in the path of the uid causing a larger amount thereof to flush across the cutting face of the bit. `When the core is broken olf, this obstruction to flow is removed and a large volume of Huid flows into the recess so as to flush the core from the bit.

Another object is to provide a bit in which a central deliberately formed core is periodically broken off and flushed from the bit by drilling Vfluid and yet the entire bottom of the hole is subjected to a clean sweep of fluid with each revolution of the bit.

Other objects, advantages and features of this invenl tion will be apparent to one skilled in the art upon consideration of the specification, claims and attached drawings, wherein:

Fig. 1 is an illustration, in perspective and partially in vertical section, ofv a drill bit constructed in accordance with the present invention;

Fig. 2 is a view of the lower end of ther bit of Fig. l;

Fig. 3 is an elevational view, in perspective, of the side of the bit viewed toward the groove or side door through which the broken-olf cores` are removed from the bit; and v Fig. 4 is a vertical section of the lower end of the bit taken on the line 4 4 of Fig. 2.

In accordance with this invention, a diamond bit is provided with a coaxial recess extending upwardly from its lower cutting surface or end so vthat as the drilling proceeds, a core will be formed in this recess., The bit is also provided with a passageway or groove extending from the recess so that as the core is broken olf in the recess, it is ilushed by the drilling uid through the groove or passageway to the exterior of the bit and need not be ground into fine pieces asin a Vconventional bit.V Since the central core is not cut away by the diamondcutting elements, therate of penetration of the bit is made essentially independent of the eiciency of cutting at the center of the bit.l

In accordance with another aspect of the invention, drilling fluid passageways and water courses are so arranged on the cutting faceof the bit that upon breaking oif a core, a relatively large amount of the fluid can flow into the core receiving recess to flush the brokerrolf core therefrom and yet while a successive core is being formed, only a small amount of fluid flows into the recess. Thus, water courses are arranged toextend across the face of the bit from inlet ports thereto to the recess.

These courses supply fluid tov flush out the brokenolf Vcores and also cause a hydraulic pressure on the cores outwardly through the smaller water courses and alsov to be distributed laterally of all of the courses across the entire face of the bit. v

Referring now to Fig. 1, there is illustrated a preferred.

form o'f the diamond drill bit.V It includes a bit body 10 having a connector, such as threaded at its senese upper end for securing the bit to the lower end of a suitable drill string. Thev bit body comprises a stock or blank 12 and a lower matrix portion 13 fixed to the stock. Imbedded in the matrix are a plurality of diamonds 14 arranged to present cutting edges to' the formation as the bit is rotated. n

While the bit body as thus far described can be made in any desired manner, one preferred manner is to machine a graphite mold or, alternatively, to machine a metal die pattern which is then used to press a bit pattern inra graphite mold. Diamonds are then carefully set in the graphite mold and powdered metal is loaded into the mold. The metal blank or stock is then landed in the powdered metal and the entire assembly heated, sintered and bonded to form a unitary structure of the blank or stock, matrix and diamonds.

However constructed, the `diamond bit will usually have a plurality of diamonds distributedabout its peripheryor gauge cutting portion 15 to cut gauge. other portion of the diamonds is distributed on the lower face or endwise cutting portion of the bit, as at 16, to cut the bottom of the hole. v

Extending upwardly from the lo'wer face 16 of the bit and coaxial with the bit body is a core-receiving recess 17. As illustrated, the cutting diamonds are disposed on the bit body about this recess so that they cut anannular portion of the bore hole and permit a core 18 (shown broken oi' in Fig. 4) to form in recess 17. This core is periodically broken off, as illustrated in Fig. 4, and removed as such from the bit. For removal of the core, a passageway is provided extending from the recess 17 to the exterior ofY and above the bit. This passageway must, of course, be located within the regular contour developed by rotation of the endwise and gauge cutting 'portions so that the core may move therethrough to a point above the bit while the bit is in a hole which it has drilled. Y As illustrated, this passageway comprises a groove 19 extending substantially radially across the lower face of the bit from recess 17 to the periphery of the bit. As here shown, groove 19 Vhas an upward extension 20 which extends above the gauge cutting surface so that the broken-off cores can move upwardly from groove 19 into' the `drill string-bore hole annulus above the bit from whence they can be carried by the drilling fluid to the surface of the earth.

To permit core removal, groove v19 has throughout its length a vertical cross-'section or depth of a size at least as large as the horizontal cross-section of recess 17 andA preferably such groove cross-section will be at .least as large as the vertical cross-section of the recess. Preferably, the side walls 2:1 and 22 of groove 19 diverge outwardly from recess 17 to reduce the likelihood of the broken-olf core becoming wedged in the groove.

As shown, vgroove 19 can be in register with one of 'attened portions 23 so 'that extension 20 need not be as deep as groove 19. The only requirement is that it be deep enough to accommodate a core between the side wall of a hole cut by the bit. and the bottomy of the groove extension 20. Any cores tending to jam in the groove extension will contact the sides of the borehole and be loosened so that they can be flushed upwardly.

Means are provided for periodically breaking o'l the core formed in recess 17. In the illustrated bit, such means "can comprise a mechanical means or a hydraulic means or both exposed to the interior of the recess, capable of exerting a lateral force on the core. the upper vend of the recess is curved, and preferably is arcuate as at 24, and constitutes such mechanical means so that as the core reaches and Vis engaged by such surface, it will be deflected laterally and broken ot thereby as illustrated in Fig. 4. It will be noted that the upper wall'25 of groove 19 merges smoothly with surface 24 and preferably slopes upwardly and outwardly to ,provide a maximum "clearance for removal of the core.

Thus,

Similarly, it is preferred that side walls 21 and 22 merge smoothly with the side walls of recess 17 and in a manner such that the juncture of these side walls with recess 17 occurs at a vertical diametral plane of the recess.

The lower end of the bit body is provided with a plurality of liuid ports or passageways 26 extending from a central bore 27 in the bit body. These ports 26 terminate at the lower end of the bit at points laterally spaced fro'm recess 17 as is best shown in Fig. 2. At least some of the ports have water courses 28 in the A.form of channels or grooves extending inwardly therefrom to recess 17. At least some of these water courses terminate in the recess at points circumferentially spaced from the juncture of the groo've 19 and the recess 17.V In this manner, fluid flowing through these water courses tends to exert a hydraulic pressure laterally on the core to break it off or toV aid in doing so. Thus these ports 26, bore 27 and water courses 28 co'nstitute a hydraulic means for breaking off the core. It will be noted that water courses 28 terminate and join recess 17 at its lower end. Accordingly, as core 18 begins to form in the recess, it tends to obstruct flow from courses 28 and such flo'w is therefore forced to be distributed over the lower end of the bit and across the bottom of the bore hole. Such distribution can be aided by scores 28a indicated Vschematically in the various views.

At least some of ports 26 also communicate with the periphery of the bit by additional water courses 29 which extend outwardly from the ports and thence upwardly along'the side of the bit. Courses 29fare made smaller in cross-section (i.e. tiow capacity) than courses 2S so that the major part of the tiud tends to ow inwardly toward recess 17. This causes considerable hydraulic pressure to be exerted on the core and to rapidly liush it from the bit after it has broken off. On the other hand, while the core is still in place, ow into the recess is restricted and a large portion of the fluid flows across the face of the bit and also out through water courses 29 for distribution over the outer po'rtion of the bottom and also over the gauge cutting surfaces of the bit.

While only one course 28 is aligned with groove 19 to exert the full force of ud pressure against the co're therein in the direction of groove Y19, the force of the fluid from all of the courses coming into the recess sums to a large component in the direction to break off the core. The strength of the formation may be so low that the pressure of the drilling fluid will breake the core before it contacts surface 24. However, regardless of what force is required to break o'l the core, the drilling Huid iius'hes it out of the bit.

It will 'be noted that the ports 26 can be spaced diterV ent distances from the center of the bit. As here illustrated, three of theports are ,shown on one circle and two on another. This Vdistribution of ports avoids a reduction of the number of cutting elements which would result if all the ports were on a single circle.

While .reference has been made herein to diamond cutting elements, other hard cutting elements can be used. However, diamonds, due to their long life, are preferred. It will also be understood that the diamonds can be arranged invarious patterns over thefaceof the bit and -its lgage cutting surfaces. Further, the ,lower end and gage cutting .surfaces of the Vbit can take varied shapes and forms .as long as the function of ,making an annular cut in the bore hole about recess 17 vis retained.

From the .foregoing it will be seen that this invention is one well Vadaptedto attain all of the -ends and objects hereinabove set forth, together with 4other advantages whichA are obvious .and -which are inherent to ,the apparatus.

It will be understood that certain features and subcombinations are of'utility andmaybe l employed without reference to other features and subcombinations. f This is contemplated by and is within the scope of the claims.

s many possible embodiments maybel made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

l. A drill bit comprising a bit body having a bit head with an endwise cutting portion and a lateral gauge cutting portion, a substantially cylindrical recess extending upwardly into the lower end of the body to a point above said endwise cutting portion and disposed coaxially therewith to receive a core remaining at the center of the hole being drilled, a core passageway in the surface of the bit body extending from said recess to a point exteriorly of and above the bit head and having a cross-sectional dimension throughout'its length at least as great as the horizontal cross-section of said recess so that la core formed in said recess and then broken off can pass through said passageway to a point above the bit, and means exposed to the interior of said recess above its lower end for applying a lateral force to an upstanding core in said recess to brake the same off.'

2. A drill bit comprising a bit body having a bit head with an endwise cutting portion and a lateral gauge cutting portion, a recess having substantially non-converging walls extending upwardly into the lower end of the body to a point above said endwise cutting portion, said recess being disposed coaxially with said bit body to receive a core remaining at the center of the hole being drilled, a core passageway extending from said recess to a point exteriorly of and above the bit body and including a groove in the surface of the bit body extending laterally from said recess to a point exteriorly of the bit body above the gauge cutting surfaces thereof and having a transverse cross-sectional dimension throughout its length at least as great as the depth of said recess so that a core formed in said recess and then broken off can pass through said groove to a point above the bit, and means carried by the bit body and exposed to the interior of said recess for applying a lateral force to an upstanding core in said recess to break the same off and for flushing such broken oft core laterally through the groove and then upwards from the bit.

3. A drill bit comprising a bit body having an endwise cutting portion and a lateral gauge cutting portion, a recess having substantially non-converging walls extending upwardly into the lower end of the bit body to a point above said endwise cutting portion to receive a core remaining at the center of the hole being drilled, said recess having a surface adjacent its upper end arranged to engage a core as it enters said recess in an axial direction and apply a lateral force to the core to deect and break the same oli, a core passageway in the surface of said endwise and gauge cutting portions of the bit body and extending laterally from said recess to the exterior of the bit body above the gauge cutting portion thereof and having a transverse cross-section throughout its length at least as large as that of said recess so that the core formed in the recess and broken off therein can pass through said passageway to the exterior of and above the bit, and means for supplying flushing fluid to said recess at a point spaced from the juncture of the passageway and recess.

4. A drill bit comprising a bit body having an endwise cutting portion and a lateral gauge cutting portion, a recess disposed coaxially with the bit body a groove extending from the top of said gauge cutting portion downwardly along the body and thence across its lower end and terminating in said recess, said recess having substantially non-converging walls extending upwardly into the bit body from its lower end so that a core can be formed in the recess by operation of the'drill, the transverse cross section of the groove at all points outwardly of the recess taken with the space overlying the groove within the regular contour developed by the rotation of said endwise and gauge cutting portions being at least as d large as the vertical cross-section of the recess so that a core formed in said recess may be flushed therethrough, and said bit body having a fluid passageway extending therethrough from its upper end and opening into said recess at a point spaced from the juncture of the groove and recess whereby flushing fluid can be directed against a core inthe recess to move it through the groove. 5. A drill bit comprising a bit body having an endwise cutting portion and a lateral gauge cutting portion, a substantially cylindrical recess extending upwardly into the body from the lower end thereof to a point above said endwise cutting portion and disposed coaxially with the bit body, said recess terminating at its upper end in an inclined dellecting surface positioned to impinge against andV break off a core formed in the recess, a groove across the lower end of the bit extending from the recess to the periphery thereof and thence upwardly, said groove having a depth throughout its length at least as great as the effective transverse dimension of the recess and having outwardly diverging side walls in its .portion extending across the lower end of the bit body so that a core emerging from the recess is prevented from jamming in the groove, cutting elements mounted on the endwise cutting portion of the body 'to make an annular cut in the formation, and means for supplying drilling uid to said recess.

6. A drill bit comprising a bit body having an endwise cutting portion and a lateral gauge cutting portion, av

recess having substantially non-converging walls, extending coaxially of and upwardly into the bit body from the lower end thereof and terminating therein for receiving a core remaining at the center o-f the hole being drilled, a core passageway extending from said recess to the exterior of and above the bit and having a transverse cross-sectional dimension throughout its length at least as great as that of the recess so that a core formed in the recess can be ushed through the core passageway, said bit body having a fluid passageway extending from the upper end of the bit into said recess at the lower end thereof and at a point spaced from the juncture of the recess and passageway whereby a core being formed in said recess tends to limit ow through said fluid passageway until the core is broken ofi whereupon resulting increased flow into the fluid passageway flushes the broken-ofi core through the core passageway.

7. A drill bit comprising a body having a bit head with a lower end drilling face, a coaxial vertically extending substantially cylindrical core receiving recess extending upwardly into said body from its lower end, a core passageway in the surface of the bit body extending from said recess to the exterior of and above the bit head and having a transverse cross-section at least as large as that of said recess so that a core broken oft in said recess can be flushed through the passageway to the exterior of the bit, said bit head having a drilling fluid supply port opening through said face at a position spaced laterally from said recess and also having a channel-like water course extending from said port across the lower end face of the bit head to said recess and terminating therein at a point circumferentially spaced from the juncture of the recess and passageway so that a core in said recess tends to limit flow of liuid from said water course into the recess to increase the hydraulic pressure applied to one side of a core in said recess. l

8. The bit of claim 6 wherein said passageway cornprises a port extending from the upper end of the bit and terminating at the lower end of the bit at a point laterally spaced from the recess and a channel-like water course in the lower end of the bit extending from the port to the lower end of the recess.

9. The bit of claim 8 wherein a second channel-like water course extends across the lower end of the bit from the port to the periphery of the bit, the second water course being of smaller cross section than that of the first-mentioned water course so that the major portion of the bit outwaidl'y to thel bits periphery,rt-he second 5 water course 'being of a smaller cross-setien than the first-mentioned water course sQ that a majolr `portion of the lluid from said port tends to ow to said Vrecess s until restricted by a core `iti the latter.

`References Cited inthe le of this patent UNITED STATES yATENTs Williams Mar. 13K, 1945 Williams Jan. 3, 1950 Kless Feb. 10, 1953 FOREIGN PATENTS 

